Abstract
Hydrates are formed of water and gas at high pressure and low temperature, conditions encountered in offshore environment. Lines plugging by hydrates is an undesirable outcome which must be avoided and has become a prevailing factor for the design and operation of subsea networks. Conventional design approach in deepwater developments consists in staying in the hydrates free domain whatever the scenario anticipated on the field. This approach often resulted in significant capital expenditure (CAPEX) with thermally insulated looped flowline, complex operating procedures having high impact on the operating efficiency and GHG emission.
This paper presents an innovative approach to manage hydrates risks in subsea developments, named NADAH (New Approach of Design Against Hydrates) and its implications for the future of offshore oil field development. NADAH is based on the understanding that some crudes have induction properties, which delay hydrate formation even when the pressure and temperature conditions reach the hydrate thermodynamic region. NADAH introduces a paradigm shift in hydrate management.
NADAH allows for mastered incursions of operating conditions into the hydrate thermodynamic region, but outside of the hydrate formation conditions, by taking into account the crude's induction capabilities at the early phase of the project. NADAH has been successfully applied on more than 5 projects, mainly in West of Africa, resulting in significant CAPEX and OPEX savings, as well as a reduction in production shortfalls and GHG emission.
For existing assets, NADAH allows simplifying the operations on site by extending the No Touch Time period and drastically delaying the requirement for any preservation operation, combining the natural capacities in delaying hydrates formation and the over-designed thermal specification. This optimization contributes to saving OPEX and production shortfalls reduction.
